The spy tactics of plants

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Light is not only essential for photosynthesis but also a crucial source of information for competing plants. An article in the March issue of Trends in Plant Science delves into the information-gathering tactics of plants which enhance their chances of survival when competition for light is high in plant canopies.

Informational photoreceptors allow plants to detect light reflected from neighboring plants and use the information effectively to forage for light in three-dimensional canopy space. Plants possess at least two types of photosensors capable of detecting light in the red/far-red ranges of the spectrum and light in the blue/ultraviolet range.

For example detection of far-red light which is scattered by neighboring plants warn a plant of the proximity of neighbors even before they begin to encroach on the actual available light. Plants respond to an increase in far-red radiation by boosting upward growth and by bending away from potentially light-hugging neighbors. Such light signaling responses not only enhance individual plant survival but also appear to improve the ability of plant communities to effectively fill up gaps in the canopy and prevent thinning of the vegetation.

This plant-to-plant signaling which uses light is now added to the other methods of communication between plants. Plant growth is also affected by signals sent by plant-to-plant contact and information passed on by volatile chemicals from infected to healthy plants. In the last case, the chemical signal prepares healthy plants against an attack by disease or pests which is affecting the infected plant. According to this review, plants are not 'vegetative' at all but active gatherers and users of information